1. Field of the Invention
This invention relates to a product for the absorption of organic compounds, and more particularly concerns a porous composite material adapted to be employed as a stationary substrate which will remove organic compounds from a fluid stream flowing through said substrate.
2. Description of the Prior Art
In the field of pollution control, it is often sought to remove toxic organic substances from fluid streams such as air and water. The organic substances may be present in dissolved, suspended or vapor form, and may be present in large amounts, or in small amounts such as in parts per million, parts per billion, or less. Exemplary toxic organic species include: polychlorinated biphenyls, dioxins, polyaromatic hydrocarbons, nitroaromatics, pesticides, herbicides, methyl t-butyl ether, and volatile halocarbons.
Current technology for removing such organic contaminants involves the use of activated carbon. However, the activated carbon, generally in granular form, must be confined within a vessel as a bed through which the fluid to be treated is caused to flow. The bed of carbon granules generally creates impedance to water flow, requiring adequate pumping to achieve a sought flow rate. Also, suspended material in an ingoing water stream may accumulate within the bed to cause even higher flow impedance. Although activated carbon functions efficiently, its total capacity for absorbed species is low, often less than 2% of the weight of the carbon. This results in the need to handle large amounts of carbon for the removal of relatively small amounts of contaminants.
In certain water treatment situations, a high impedance to the flow of water through a stationary bed of absorbent material cannot be overcome merely by increasing pumping pressure. Such situations are generally encountered in passive, unattended or in-situ remediations of water which flows by gravity effect alone. Typical examples of such remediations include treatment of stormwater, landfill leachate, and end-of-pipe industrial and agricultural discharges.
In practical applications wherein trace components are removed from a flowing stream, it is desirable that the sought degree of removal be achieved with minimal requisite time of contact of the stream with the absorbent bed. When employing granular activated carbon to remove species from a water stream, contact times of over ten minutes are often required. Further shortcomings of the use of granular activated carbon are the lack of selectivity for toxic compounds, and handling difficulties in loading and unloading the carbon into absorption vessels. One factor in causing such handling difficulties is the relatively high bulk density of granular activated carbon.
U.S. Pat. No. 6,306,488, issued Oct. 23, 2001 describes the selective removal of dissolved chlorocarbons in a brief residence time and with low flow impedance using a composite porous structure comprised of hydrophilic microporous polyvinylchloride (PVC) deposited within cubes of cellulosic sponge. Although effective in use and easier to handle than granular materials, the cellulosic sponge component of said composite structure is relatively costly.
It is accordingly an object of the present invention to provide an absorbent product useful for the rapid removal of toxic species from a fluid stream.
It is another object of this invention to provide an absorbent product as in the foregoing object which can be employed as a stationary bed through which a fluid is caused to flow.
It is a further object of the present invention to provide an absorbent product of the aforesaid nature which, in bed form, presents minimal impedance to the flow of said fluid.
It is yet another object of this invention to provide an absorbent product of the aforesaid nature having a relatively low bulk density.
It is a still further object of the present invention to provide an absorbent product of the aforesaid nature which can exist as a self-supporting shaped structure.
It is an additional object of this invention to provide an absorbent product of the aforesaid nature amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.
The above and other beneficial objects and advantages are accomplished in accordance with the present invention by a self supporting porous composite structure having absorptive affinity for chlorocarbon compounds in fluid streams and comprised of a multitude of water absorbent particles of cellulosic origin interbonded by hydrophilic microporous PVC. In a preferred embodiment, the invention is comprised of a multitude of said structures useful as a bed through which a fluid is caused to flow with low impedance.